Sensitivity Dependence of Single Nanoparticle Mass Detection Using Mechanical Oscillations in Optical Microcavities

Single nanoparticle detection is demanding in fields such as early-stage diagnostics, environmental monitoring and biochemical researches. Microcavities are becoming excellent platforms for ultrasensitive detection due to the extremely strong enhancement of light-matter interactions. However, the analytes to be detected will introduce optical losses, which eventually spoils the detection limit of the optical sensor. The strong light confinement enables optical induced mechanical oscillations that is also sensitive to analyte attachments and can thus be applied as an alternative sensing signal in microcavity sensors. In this work, the mass sensitivities of the mechanical oscillations of a microcavity are theoretically discussed. The sensitivity dependence on different modes, analyte sensing position and microcavity structure are explored via finite-element-method simulations, which are consistent with theoretical predictions. Our results provide an effective guideline for the sensitivity optimization during microcavity design aiming for single nanoparticle mass detection.